Wouldn't it be ironic if the AGW defense to that scenario actually playing out is that it's just "regression to the mean" and therefore warming is still happening!

But back on topic - is there any way in which AGW is a falsifiable hypothesis? I can't think of a way to falsify it, but then it's the proponents who should be telling us how they are trying to falsify it. All good scientists try as hard as possible to prove themselves wrong.

I don't see it as science in itself, since as I understand it the hypothesis is based on the idea that CO2 and other greenhouse gases are causes of the observed warming in the last couple of centuries or so. I see computer modellers as in the same class as chemistry lab. glass-blowers or physics lab. machinists - highly skilled and essential technicians but not scientists.
You can use a computer model to reproduce almost any past behaviour by judicious choice of coefficients and parameters but, like Ptolemy's epicyclic model of the solar system, its output will start to diverge from reality as soon as you move into the future.
What we are seeing at the moment is global cooling, which the True Believers quite rightly point out is part of a decadal-scale oscillation (probably) superimposed on a centennial-scale rising trend. Where they and I diverge is their acceptance of the rising trend as being due to GHGs emitted by H. sap. I see it as part of a millenial-scale oscillation, quoting as evidence the past records of the last half-dozen or so interglacials.
True believers will also quote as evidence of man's involvment the C12/C13 ratio which they say proves that the excess CO2 is the result of fossil fuel burning. I agree that the C12/C13 ratio is rising because most of the CO2 being released is from carbon locked away by photosynthesis (i.e. with more C12) but this means nothing because fossil fuels were also produced by photosynthetic processes.
The real problem True Believers have is the 800-year time lag between temperatures and CO2 levels in each of the deglaciations that we know about. Their concentration on the beginning (temperatures start to rise because of some other influence, so CO2 is released from solution, peat bogs decay and permafrost melts leading to positive feedback) rather gives away their awareness that such a scheme will inevitably lead to thermal runaway (as all positive feedback must) unless "some other factor" then causes temperatures to fall for 800 years or so until CO2 levels start to fall.
Much is made of the natural flux of carbon, with New Scientist publishing a graphic showing natural CO2 emissions of 430GT per year being balanced by absorptions of 430GT until those wicked industrialist came along and put 26GT per year in. Ignoring for the moment the validity of the actual figures (man's output could be fairly accurate, as the coal and oil are taxed), can you think of any natural system which has not swung hard on or off aeons ago in which absorption so precisely balances emission and is not capable of matching a 5% variation? I can't
So, returning to the original question, yes, AGW is a scientific theory in that it can in principle be disproved if only post facto. To my mind the last set of deglaciations have done that.

I agree with you that the AGW arguments are of the type that are so 'flexible' that they are not provable at this time. Indeed it may take a century or so of 'believable' measurements before anything could be considered as being rigourously scientific.

If one was looking for the ultimate Catch 22 scam AGW would have to be a great model irrespective of whether there is any provable cause and effect in the long term.

The idea of going to a bookie and asking for odds is merely a way of obtaining an external independent assessment hypothesis that just might help to narrow the focus into areas that could be considered in scientific method in the future.

I assume it would not be impossible to conduct a whole world experiment to see what would happen if a significant CO2 production was enacted for, say, a year. But the knock on effect for people's lives might introduce some negative reactions.

So in a way I think we might say that the theory could in part be tested - both reduction and increase of human produced CO2 could be governed in theory - but the chances of being able to set up the experiment are tiny. (Understatement)

Get the models to predict what is going to happen 6 months from now. See how they fair. If it passes muster, use it to prognosticate further into the future. Say a year, with quarterly feedback. How much precipitation will the North Sahara receive? The Northwest Territories? The Southwest United States? What will the average temperature be during each month?

This may not be falsification, but it might help create models that can predict the future climate. At the very least it might make everyone realize that there model is little more than a dice roller.

Predicting the Climate in the near future has HUGE financial benefits. If a city can plan ahead knowing that 4 ft of snow is going to fall in the month of February, they can make sure equipment is up and running, labor is ready to move and resources are standing buy Just in Time.

Every time I suggest this to a Proponent of AGW, they go silent. I don't know if it is because they think I am nuts or cognitive dissonance is forcing them to avoid the subject.

My view of climate science is that it is science, but it's a form of applied science, and a rough type of applied science, rougher than engineering.

I see climate science as being part of a bunch of subjects thaat might be classified as 'risk analysis' or 'risk modelling'. The demand for risk analysis comes from the increasing safety culture of the modern age and this type of work is typically requested by regulatory agencies, governments and the insurance industry. Risk analysis often tends to involve speculative computer models and the guessing of suitable input data.

I'm a bit puzzled as to why scientific bodies endorse climate science as much as they do. These scientific bodies tend to represent pure science and operate a demarcation line with the most well known form of applied science, engineering. Why are they endorsing an even rougher type of applied science?

On the falsification issue, I actually don't think it's essential, though it may be desirable, that a scientific theory can be falsified. The theory of evolution isn't easy to falsify at all, apart from the obvious falsification case of a deity with supernatural powers suddenly turning up. The more scientifically educated creationists often use the falsification argument to claim that evolution isn't a scientific theory. The originator of the falsification idea, Karl Popper, is supposed to have said at one time that “Darwinism is not a testable scientific theory, but a metaphysical research program” but later on he announced that he had changed his mind, possibly under pressure from others. Personally I think evolution is a very good scientific theory, despite the fact any falsification is very difficult and that it also has a very limited predictive capability, because the only other theory on the table covering this area, religion, looks terrible in comparison.

Lubos Motls, the science blogger and AGW sceptic, gave a pretty good critique of falsification and Karl Popper in a blog post earlier this year. He was responding to a New Scientist article attacking theoretical physics using the falsification argument.

The story goes that Karl Popper invented his falsification-based scientific method basically because he was worried about how certain individuals seemed to be misusing the traditional induction-based scientific method. Karl Marx tried to claim Marxism/Communism was a scientific theory on the basis that he'd worked it out by induction from observations. Sigmund Freud invented the soft science of psychology by inducing it from observations. So Popper came up with a new version of the scientific method that he hoped would scupper Marx and Freud. But I don't think many people ever seriously believed Communism was a scientific theory and the rise of psychology hasn't been stopped.

You're talking about the famous "Precambrian rabbit fossil" there. I've heard that was invented to fob off a 'Popper zealot'. Popper has quite a substantial 'fan club'. A few years ago the Sp!ked website ran a survey called something like "If you could teach the world one thing", where people were asked to impart some piece of knowledge to others they thought was crucial. The Popper falsification idea, to my surprise, turned out to be one of the most popular pieces of knowledge. So I can understand that Dawkins may feel obliged to come up with something to satisfy the Popper followers.

The follwing link gives a fairly good discussion about whether it really would falsify evolution:

Evolutionary biologist Richard Dawkins said that the discovery of fossil mammals in Precambrian rocks would "completely blow evolution out of the water."[14] However philospher Peter Godfrey-Smith doubted that a single set of anachronistic fossils, even rabbits in Precambrian, would disprove the theory of evolution. The first question would be whether the alleged Precambrian rabbits were really fossilized rabbits. Alternative interpretations include incorrect identification of the "fossils", incorrect dating of the rocks and a hoax such as the Piltdown Man was shown to be. Even if the Precambrian rabbits turned out to be genuine, they would not instantly refute the theory of evolution, because that theory is a large package of ideas, including: that life on Earth has evolved over billions of years; that this evolution is driven by certain mechanisms; and that these mechanisms have produced a specific "family tree" that defines the relationships between species and the order in which they appeared. Hence Precambrian rabbits would prove that there were one or more serious errors somewhere in this package, and the next task would be to identify the error(s). Benton pointed out that in the short term scientists often have to accept the existence of competing hypotheses, each of which explains large parts but not all of the observed data. "

In terms of falsifying AGW, one possible scenario that I think the AGWers might accept would be that background CO2 levels suddenly started to go down significantly.

As a follow-up to my previous post on the Precambrian rabbit,it might be useful to note (though it's going even more off-topic) that the Precambrian rabbit situation has actually occured in physics.

There have been two equivalents of the Precambrian rabbit in the theory of light (and electromagnetic radiation in general). One is that the carrier medium for light, "the aether", can't be detected and is no longer assumed to exist. The wave theory of light is however still retained because it appears to be successful in what it does, but it can't be correct if the waves travel in nothing. Something has to be waving. The second Precambrian rabbit is the realisation that light shows particle-like behaviour in certain situations, and this has been absorbed into something called 'particle-wave duality'. But the particle or corpuscular theory of light was actually falsified in an experiment in the 19th century by Foucault when he showed that light travels at a slower speed in water than in air. The whole idea of particle-wave duality sticks two fingers up at Popper.

Now there is a mechanism for propagation of light which doesn't need an aether and which could explain particle-wave duality, but it's too far-fetched to contemplate. This mechanism assumes light doesn't actually travel, it gets from atom A to atom B as an oscillating force by action-at-a distance. Newton's gravity uses the idea of action-at-a distance, but for light it would be a lot more complicated because light has (or appears to have) a definite speed associated with it and unlike gravity not all matter is transparent to light. This mechanism is called 'retarded action at a distance' and atom A would somehow have to 'know' how far atom B was away from it to adjust the time delay in sending light to B. On top of that, if an object that isn't transparent to light was inserted between A and B, atom A would have to recognise this situation and not send anything to B.

Given that precedent from the world of physics, I think evolution theory could handle a Precambrian rabbit situation.

I think the point of the falsification argument is that it is at least possible to falsify evolution in principle. Of course, if you accept that it is never possible to know something with 100% certainty it is also not possible to falsify anything with 100% certainty - so the question is one of degree. A rabbit fossil as old as life itself would falsify evolution, notwithstanding the caveats that you mentioned and that one would be obliged to attach to such falsification. I am looking for how AGW can be falsified in principle. If there is no way to falsify AGW in principle, that seriously undermines the value of the hypothesis.

I see AGWers investing a lot of effort in trying to persuade me that they are right. I don't see them investing much effort in trying to persuade themselves that they are wrong - and back when I were a scientist, my alleged poverty of ejumucation notwithstanding, I did the exact opposite.

"I see AGWers investing a lot of effort in trying to persuade me that they are right. I don't see them investing much effort in trying to persuade themselves that they are wrong - and back when I were a scientist, my alleged poverty of ejumucation notwithstanding, I did the exact opposite."

One of the common explanations for that particular observation is one that drifts somewhat into conspiracy theory territory. In the past few decades there has been a rise in what might be called "ethical science" or "Green leaning science". This webpage about a UK organisation called "Scientists for Global Responsibility" (SGR) gives some details about ethical science.

One of the career paths that ethical scientists like to go into is climate science. The founder of SGR, Stuart Parkinson, is himself a former climate scientist. The Climate Research Unit, Hadley Centre and Tyndall Centre are all listed as organisations that are considered to be 'ethical' on SGR's ethical employment contacts webpage.

A little knowledge is a dangerous thing, or so it is said, and the problem one might see is that pronouncements are often made with certainty when in fact we have no easy or reliable way to measure out total 'knowledge', thought one might be talking from a point of 100% familiarity with the present state of knowledge.

Evolution is often presented as something happening over unimaginably long time scales - but is that true? Is the ability to measure accurately back in time so good that it can remove any doubt about estimates of measurement?

In what we think of as geological time scales there can be quite obvious evolutionary development in a species, or not much at all. If one thinks of human development as something that has occurred over, say, a 1 million year period such developments could have occurred more than once in the life of the planet and be lost in the noise. Even in what we might think as recent times.

Given the same kind of environment the potential for extremely similar evolutionary development without a continuous link for the species between the periods could not be ruled out.

On the other hand Creation proof would require the identification of a actor that had the ability to create directly in some way OR by running a process from raw materials and having some controlling influence (perhaps imperfect) over the subsequent evolution.

The identification of such an actor would give a strong boost to creation as a concept but still not exclude evolution as a truth. It would simply be a truth after creation.

I have no reason to suppose the 'humans' have not been around several times and then disappeared again in the geological past. Proof of that, or even the potential for it to be likely, would require luck since any evidence we are likely to understand would mostly have been destroyed by ice ages and other planetary events. We cannot recreate the experiment and expect to survive it to observe the result so have to work on the balance of probability. That's a judgement call. So it is with the AGW hypothesis, IMO.

I had my concerns that this might end up focusing on something other than AGW, but here goes.

We observe life and seek an explanation as to why we observe life. The "hypothesis space" is essentially infinite - limited only by reality, and within reality limited only by human imagination and ingenuity. But we need only concern ourselves with those hypotheses which have so far been stated, and we can conclude (A) one of the hypotheses is sufficiently close to the actual truth to be useful, (B) none of the hypotheses are of any use and someone needs to do some more work. Assuming (A), we can then state reasons as to why we find certain hypotheses to have a close to 0% probability of being correct and why we find one of them to have a >>0% probability of being correct, or at least not wrong.

No one would claim that the current understanding of evolution is absolutely correct and will remain unchanged for all time, but the weight of expectation is that it is far more likely that the theory will move incrementally towards a perfect description of reality in ever smaller steps without ever getting to its destination, than that God will come down from his heaven on judgment day and tell us we have got it all wrong.

AGW seems to me to pull a number of stunts which bypass this process altogether. Firstly, what observation are we trying to explain? It seems to me the observation that AGWers are trying to explain is largely something that they predict we will observe over the next 100 years rather than something we have already observed (and that many of the expected observations such as hurricanes inundating cities built below sea level in hurricane-prone areas, are pretty much dead certs over a 100-year period.) Secondly, if there is a observation that needs explaining (e.g. warming between 1980 and 1998 which almost no one disputes actually happened), what are the other ideas in town? Proponents of evolution at least acknowledge the existence of crackpot religious ideas and the more patient evolutionists expend considerable effort on explaining why the crackpot religious ideas have a close to 0% probability of being correct. AGWers simply dismiss alternative hypotheses without a second thought (in much the same way that religious crackpots dismiss evolution without a second thought). Even if the suggestion that that warming was not anthropogenic in origin is totally crackpot, someone should be able to provide a thoughtful explanation as to why.

Your point about humans potentially having evolved many times is taken. It's a possibility, but a rather remote one. Evolution works by applying selection to (effectively) random genetic changes and it is vanishingly unlikely that near enough the same thing will happen twice, especially at a distance of time with very different circumstances.

I agree. With everything you wrote including the vanishingly small potential that there is likely to have been almost identical instances of human evolution separated by periods of huge change that resulted in different basic circumstances existing at possible starting points.

Very unlikely indeed. But still difficult to disprove.

I could extend it and say there may have been 'similarities'.

Perhaps humanity has not so much evolved from a previous distinctly different biological state more than once but may have evolved once and become highly developed as a social and knowledgeable civilisation (in a modern way we could understand) and then failed for some traumatic reasons - too much carbon sequestration perhaps or maybe galloping temperature tipping points, any reasons, does not matter what - and resulted in ALMOST total destruction but some survived and returned to regenerate another version of 'civilisation' developed over time from a new blank mind. (Or not ...)

Alternatively humanity has not existed previously but creatures with similar abilities to invent and adapt to a greater extent than other creatures and perhaps use tools and some equivalent of science for their own betterment .... and so on.

As with AGW there is always the potential that some event might prove to be a decisive proof, one way or the other, that such events did in fact occur, but the chances of that are very very small based on out current knowledge, skills and potential for radical discoveries. AGW is the same, in my opinion, other than the effective battle ground is the future rather than the past. Whilst that might suggest a greater potential for improving and refining the knowledge available to come closer to refining the hypothesis in much shorter geological time scales it may equally prove to pose more scientific questions (based on new knowledge) than are answered.

Perhaps the problem lies not with science and scientific principles but with the concepts of working with them reliably detached from any other influences so that over time the target question at least remains the same (as it likely does most of the time with fundamental historically oriented questions.)

But that won't happen so it will come down to a moving target of what people are trying to prove. Or rather many targets I would suspect. None of them are likely to be absolutely provable without large error bars and nor are the moving targets, billed as 'future', likely to be disprovable in a reasonable (if any) period of elapsed time. The entire theory, from a social context, seems to rely on that being the case 0 in which event it can hardly be considered scientific.